Modernization of F. Hoffmann-La Roche Ltd's Historic Basel Site: Construction of Building 2

As part of the modernization of its historic site in Basel, F. Hoffmann-La Roche Ltd is erecting Building 2: this office building will be 205 m tall and located directly opposite the new Building 1, which is already in operation.

After the demolition of the existing Building 43, the construction of Building 2 required an excavation pit of 20 m deep (10 m below the groundwater table) as well as 103 large bored piles (d=1.5 m) as foundation piles on an area of 2,400 m². Because of risks of settlements damages in the surroundings and due to lack of space, anchors could hardly be implemented to support the excavation pit. Instead a bracing plate was designed (modified top-down method). For the highly stressed intersected bored pile wall, the primary piles had to be reinforced with HEM800-S355 steel beams (in addition to the reinforced secondary piles) to increase the bearing capacity.

The foundation consists of a combined piled raft foundation (CPRF) to reduce the settlements of Building 2. The foundation was computed with 2 coupled finite element models (structural and geotechnical models). These models have been iteratively and automatically matched with a self-written procedure. The input parameters of the 3D-FE-models were calibrated according to the long-term measurement results of the neighboring high-rise Building 1 - also founded on a CPRF. In addition, several static and dynamic pile tests of Building 1, which were carried out up to failure, were used for a better calibration of the ground parameters.

Services provided by Gruner Ltd's Geotechnical Engineering Department and Gruner Lüem AG comprise:

• Planning for the following phases: preliminary design, basic design, detailed design, tendering
• Demolition/deconstruction, excavation pit, combined piled raft foundation, bracing slab
• Deformation forecasts and monitoring for the excavation pit, foundation and neighboring buildings due to the excavation of the pit, dewatering, construction of piles and anchors, building construction
• Construction management for the demolition, excavation pit, foundation, bracing slap

Services provided by Gruner Ltd's Structural Maintenance Department comprise:

• Crack-monitoring, preservation of evidence, monitoring of noise and vibrations

Publications regardiing this project:

• Pitteloud, L.; Meier, J.; Hebecker, R. (2020): Unter dem zweiten Turm. Espazium. link pdf
• Pitteloud, L.; Meier, J.; Hebecker, R. (2020): La face cachée de la Tour 2 du Groupe Roche à Bâle. Tracés, Vol: 146, No: 4, S. 27-31. pdf
• Pitteloud, L. (2020): Bien fondée pour aller plus haut. Chantiers Magazine, Vol: 49, No:3, S. 35-41. pdf
• Pitteloud, L.; Meier, J. (2017): Statische und dynamische Versuche an Bohrpfählen in der Molasse im Raum Basel. Burgdorfer Geotechniktag 2017 - Beobachtungsmethode und Monitoring in der Geotechnik, Berner Fachhochschule, Burgdorf, 19.01.2017. pdf
• Pitteloud, L. (2012): Pfahlbemessung nach SIA 267 – Erfahrungen aus der Praxis. Frühjahrstagung der Geotechnik Schweiz, 10.05.2012, Olten, Pages 77 - 90. pdf

Further publications: https://www.gruner.ch/en/discover/geotechnical-engineering

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